Engineering Chemistry S Datta

POLLUTION PREVENTION AND WASTE MINIMISATION 585
2. Air. Generally radioactive gases are stored in tanks, buried in the ground and finally
vented to air so that there is low level of activity in the air, otherwise it may be
inhaled and may enter the living system.
3. Water. For long term disposal ultimately the wastes are encased in non-corrosive
lead, titanium or copper containers and burried deep into the ocean. It must be secured
or it may affect the aquatic life, fishes and enter the food chain or enter the
ground water.
Radionuclides
Radionuclides are the products of the natural decay of uranium. Uranium tailings contain
a variety of radioactive atoms or radionuclides like, Ra-226, Th-230, Pb-210 etc.. Some of these
have long half lives, e.g., Th-230 has a half life of 80,000 years. Depending on the pH of the
tailings, these nuclides become soluble and available.
The main exposure pathways for radioactivity from tailings are γ radiation, inhalation
of radioactive particulates, radionuclides entering the food chain. There are more than 1000
radionuclides in the atmosphere. Both the long life and short life types of nuclides are of
concern for public health problems. The table below indicates the active sites for and the halflife
of different radionuclides.
Table 27.1. Some Important radionuclides and their half -lives
Radionuclide Target tissue Half-life
Calcium-45 Bone 165 days
Carbon-14 Whole body 5760 years
Caesium-137 Soft tissue, genital organs 27 years
Iodine-129 Thyroid 17 million years
Iodine-131 Thyroid 8 days
Plutonium-239 Bone, liver, spleen 24,400 years
Radium-226 Bone 1620 years
Strontium-90 Bone 28 years
Tritium ( 3 H) Whole body 12.3 years
NOISE POLLUTION
Discomfort caused by hearing unpleasant, undesirable sound at wrong places and at
wrong times is called “noise pollution’’. Noise pollution is expressed in Decibel units (dB). The
smallest sound unit audible and undisturbing to a healthy person having good hearing capacity
is ‘‘one decibel”.
Crowded cities, mechanised transport, heavy industries, modes of entertainment cause
noise pollution.
Sources of Sound Pollution
Heavy automobiles, scooters, trains, aeroplanes, horns, sirens, factories, loud speakers,
radio, TV, air conditioners, generators, different functions and meetings are the different sources
of noise pollution.
WHO has recommended that a person can sleep upto 35 dB noise, 75 dB is the explosive
limit, 80 dB is harmful, damaging the hearing system.